Suggest you not get started with Perl::Unit at all. :)
You see, Perl::Unit aka Test::Unit appears
to have been abandoned,
Note that, unlike Perlish-mainstream Test:: modules, Test::Unit is not based on Test::Builder.
A common mistake I've seen from folks coming from a
non-Perl xUnit background
is to use Test::Unit in preference
to the Perl-mainstream and much more widely used Test::Builder/TAP/Test::More/Test::Class set of
modules ... only to regret that decision later.
Have a read of the "Other Modules for xUnit Testing in Perl" section of the
documentation, which compares Test::Class with
other xUnit-style Perl testing modules (including Test::Unit and Test::SimpleUnit).